The present application is based on and claims priority from the following Japanese Patent Applications: 2002-77774, filed Mar. 20, 2002 and 2002-117775 filed Apr. 19, 2002, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a compact and powerful rotary electric machine to be used for a passenger car, an airplane and an electric power tool.
2. Description of the Related Art
A typical rotary electric machine to be used for a vehicle is an alternator that has a Lundell type rotary magnetic core. The Lundell type rotary magnetic core is composed of a boss portion, a pair of disk portions disposed at opposite ends of the boss portion and a plurality of claw poles extending from the disk portions in the axial direction of the core to alternately interleave with each other. A cylindrical field coil is wound around the boss portion to supply magnetic flux to parallel magnetic circuits that respectively include the claw poles. Therefore, comparatively large magnetomotive force can be applied to the claw poles, so that the alternator can generate comparatively high power.
However, the thickness of the claw poles have to be limited in order to limit the outside diameter of the alternator. This limitation may cause DC magnetic saturation, which limits an amount of effective magnetic flux and output power of the alternator.
In order to increase the effective magnetic flux, it has been proposed that a permanent magnet is inserted between adjacent claw poles. However, the space for accommodating the permanent magnets is limited and cooling performance of the alternator may get worse because the permanent magnets close air passages.
Therefore, a main object of the invention is to provide a more compact and powerful rotary electric machine.
According to a feature of the invention, a rotary electric machine includes an armature core and an armature winding mounted in the armature core, a rotor having a rotor core, a rotary magnetic-flux source fixed to the rotor core, a frame and a stationary magnetic flux source fixed to the frame. The stationary magnetic flux is supplied to the rotor core in a direction to supplement the first magnetic flux. Therefore, effective magnetic flux supplied to the armature core can be increased without increasing the size of the rotor. Because the stationary magnetic source can be disposed in a dead space of the front frame, the frame does not increase the size. The second magnetic flux source may include a yoke for magnetically connecting the armature core and the rotor core and a stationary field coil for providing dc magnetomotive force in a direction opposite the polarity of the rotor core. The rotary or stationary magnetic flux source may be composed of a permanent magnet. In such a case, the other includes a field coil. The field current supplied to the field coil is controlled to change magnetic flux supplied to the armature core.
Another object of the invention is to provide an electric rotary machine whose rotor has a reduced moment of inertia in order to rotate as soon as it is started.
According to another feature of the invention, a rotary electric machine includes a stator core, a three-phase armature winding and a field coil, an inductor rotor disposed opposite the stator core via a first air gap and a magnetic circuit means for connecting the rotor, the stator core via a second air gap. The inductor rotor is composed of a plurality of magnetically conductive portions and magnetically non-conductive portions that are alternately disposed in the circumferential direction thereof between the first air gap and the second air gap.
Because the inductor does not include a cylindrical field coil or claw poles, the moment of inertia thereof is very small as compared to the rotor having a Lundell type pole cores. When the motor-generator is operated as a motor, the inductor can rotates in a very short time after armature current is supplied by the inverter because of the small moment of inertia of the inductor.
The inductor rotor may include a plurality of permanent magnets having the same polarity disposed in the circumferential direction thereof at two magnetic pole-pitches. The field coil may be disposed inside the inductor rotor.